The challenges of thin Cu Wire Bond on thin FSM and small BPO

With the industry trend moving towards miniaturization and cost reduction, Wire size and Front side metallization (FSM) become thinner and Bond Pad Opening (BPO) getting smaller as well. This paper specifically discusses the challenges and countermeasures being done during the optimization for thin Cu wire (25um) on thin front side metallization (1.6um AlSiCu) with small bond pad opening (65um) where these challenges include NSOP, inconsistent ball size, cratering and metal peeling have been successfully overcame through the capillary design, clamp and heater plate design and WB parameter optimization. Small BPO required special shearing method which is “passivation shearing” also briefly discussed. Reliability stress test (PC+AC 96 hr, PC+TC 1000x and HTS 1500hr) was perform with positive result.